Overlooked in this is Rubio's big Achilles' heel: his record. Not his legislative record -- though Democrats would surely take great pains to paint him as an extremist, he tends to be in the mainstream of the GOP -- but his political and lifestyle ones. Those areas will give opponents plenty to work with. There's no single smoking gun -- the lone revelation that would make him unviable. Instead, his record raises a series of smaller questions that would add up to many potential headaches for a campaign headed into a tough election against an incumbent president. The case for Rubio is well known, but here's a quick rundown on his potential vulnerabilities.

"I’ve said it before. I’ll say it again. The DREAMers are our neighbors, they're our friends. They are our high school valedictorians, and they are our veterans. They were brought to this country before they ever even knew of the significance of their trip, and they have benefited our communities greatly. And so it's clear that America is stronger for a person like Elisha Dawkins. And as this Congress comes to a close, I want to remind all of us and urge us to remember next year, when there's an attempt to turn around that White House executive order, I want us to remember the faces of people like Elisha Dawkins, and I want us to come together and to acknowledge their many contributions to this great country." —Sen. Bill Nelson